Influence of energy efficiency on VOCs decomposition in non-thermal plasma reactor

In order to promote the plasma technology for commercial application and improve the energy efficiency of non-thermal plasma, a series of experiments on energy efficiency of plasma reactor were carried out for volatile organic compounds removal. This research adopts a pipe-line reaction device with plasma generated by dielectric barrier discharge technology to examine the effects of different experimental parameters, including medium packing, electric field strength, the pollutant initial concentration, and gas velocity, on the energy efficiency. In the study, four kinds of packed materials were packed into the plasma reactor: a complex catalyst, Ba_0.8Sr_0.2Zr_0.1Ti_0.9O₃, MnO₂/γ-Al₂O₃, and γ-Al₂O₃. Through optimizing the experimental parameters, the best decomposition efficiency of toluene and the best energy efficiency were achieved. The experimental results show that the energy efficiency has a trend from increasing to decreasing with increasing pollutant gas velocity, and the energy efficiency changes from increasing to decreasing with the increasing of initial concentration of pollutants, and the decomposition efficiency and the energy efficiency have the same order from high to low with different packed materials in the plasma reactors, in turn, packed with complex catalyst, Ba_0.8Sr_0.2Zr_0.1Ti_0.9O₃, MnO₂/γ-Al₂O₃, γ-Al₂O₃ and no padding. The optimized parameters for toluene decomposition are: the gas flow rate of 2 mL/min, the initial concentration range of 1500–2000 mg/m³, the field strength intensity of 9.6 kV/cm, and the plasma reactor packed with a complex catalyst, which results in the best energy efficiency of 10 g/kWh. This research provides not only a new way to develop the plasma technology, but also a reference for the commercial application.     

天然勃姆石热相变体γ-Al2O3交换氟离子的研究

天然勃姆石矿在适当焙烧条件下可相变成γ-Al₂O₃,而γ-Al₂O₃,具有吸附水体中F^-的性能。吸附F^-后可用稀NaOH溶液解吸,酸中和再生。解吸后的含氟NaOH废液可用石灰粉回收,既减少了NaOH的消耗,又避免了对环境的污染。     

Influence of hydroxybenzoic acids on the adsorption of Eu(III) onto α,γ-Al2O3 particles in mildly acidic conditions: A macroscopic and spectroscopic study

The influence of hydroxybenzoic acids (HAH_n), namely p-hydroxybenzoic acid (4-hydroxybenzoic acid, HPhbH) and protocatechuic acid (3,4-dihydroxybenzoic acid, HProtoH₂), on the adsorption of europium(III) onto α,γ-Al₂O₃ particles is studied as a function of acid concentration. After measuring the adsorption edge of the Eu(III)/α,γ-Al₂O₃ binary system, and using the previously studied binary component system Eu(III)/HAH_n—Moreau et al. (2015) Inorg. Chim. Acta 432, 81—, and HAH_n/α,γ-Al₂O₃—Moreau et al. (2013) Colloids Surf. A 435, 97—, it is evidenced that HPhbH does not enhance Eu(III) adsorption onto α,γ-Al₂O₃ in the Eu(III)/HPhbH/α,γ-Al₂O₃ ternary system. Conversely, HProtoH₂ enhances Eu(III) adsorption onto α,γ-Al₂O₃ in the Eu(III)/HProtoH₂/α,γ-Al₂O₃ ternary system. Adsorption of the acids are also found higher in the Eu(III)/acid/α,γ-Al₂O₃ ternary systems as compared with the corresponding binary systems assessing synergetic effects. For high HPhbH concentrations, a ternary surface species involving ≡AlOH surface sites, Eu(III), and PhbH^– is evidenced by time-resolved luminescence spectroscopy (TRLS). However, in the Eu(III)/HProtoH₂/α,γ-Al₂O₃ ternary system, chemical environment of Eu(III) is found to be very close to that in the Eu(III)/HProtoH₂ binary system. Ternary surface species could not be evidenced in the Eu(III)/HProtoH₂/α,γ-Al₂O₃ ternary system with TRLS because of the very short decay time of Eu(III) in the presence of protocatechuic acid.     

Comparison of Mo/MgO and Mo/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts: impact of support on the structure and dibenzothiophene hydrodesulfurization reaction pathways

The MgO and P₂O₅-promoted γ-Al₂O₃ supports with alkaline and acidic natures, respectively, were prepared, impregnated with Mo atoms, and compared for dibenzothiophene (DBT) hydrodesulfurization (HDS) reaction. Ultraviolet spectroscopy and the principal component analysis were used to identify the impact of the supports on the reaction pathways. The catalysts were characterized by BET surface analysis, X-ray diffraction, temperature-programmed reduction, Fourier transform infrared, and X-ray photoelectron spectroscopy. The γ-Al₂O₃-supported catalyst favors the hydrogenation pathway relative to the MgO-supported catalyst, which facilitates the direct desulfurization route. The different performance was attributed to the dissimilar Mo phases that emerged during the activation procedure. The activation under sulfo-reductive condition changed the Mo atoms on γ-Al₂O₃ support into the sulfide phase while extra oxidation took place for the MgO-supported catalyst. The migration and consumption of loosely bonded bulk oxygen atoms with under-coordinated Mo atoms on the MgO support were introduced as a possible reason for such extra oxidation. DFT calculations predicted an interaction between the Mo/MgO catalyst and DBT via the electron donation from the catalyst oxygen atoms to the aromatic rings, resulting in weakening and breaking of the C–S bonds. In spite of the higher resistance of the MgO-supported catalyst toward coking and its superior activity, its lower hydrogenation capability suggested using a dual-function catalyst. Accordingly, two catalysts were mixed and the synergism was observed in the HDS reaction of thiophene.     

A multi-analytical study of the crystal structure of unusual Ti–Zr–Cr-rich Andradite from the Maronia skarn, Rhodope massif, western Thrace, Greece

Unusual Ti–Cr–Zr-rich garnet crystals from high-temperature melilitic skarn of the Maronia area, western Thrace, Greece, were investigated by electron-microprobe analysis, powder and single-crystal X-ray diffraction, IR, Raman and Mössbauer spectroscopy. Chemical data showed that the garnets contain up to 8 wt.% TiO₂, 8 wt.% Cr₂O₃ and 4 wt.% ZrO₂, representing a solid solution of andradite (Ca₃Fe³⁺ ₂Si₃O₁₂ ≈46 mol%), uvarovite (Ca₃Cr₂Si₃O₁₂ ≈23 mol%), grossular (Ca₃Al₂Si₃O₁₂ ≈10 mol%), schorlomite (Ca₃Ti₂[Si,(Fe³⁺,Al³⁺)₂]O₁₂ ≈15 mol%), and kimzeyite (Ca₃Zr₂[Si,Al₂]₃O₁₂ ≈6 mol%). The Mössbauer analysis showed that the total Fe is ferric, preferentially located at the octahedral site and to a smaller extent at the tetrahedral site. Single-crystal XRD analysis, Raman and IR spectroscopy verified substitution of Si mainly by Al³⁺, Fe³⁺ and Ti⁴⁺. Cr³⁺ and Zr⁴⁺ are found at the octahedral site along with Fe³⁺, Al³⁺ and Ti⁴⁺. The measured H₂O content is 0.20 wt.%. The analytical data suggest that the structural formula of the Maronia garnet can be given as: (Ca_2.99Mg_0.03)_Σ=3.02(Fe³⁺ _0.67Cr_0.54Al_0.33Ti_0.29Zr_0.15)_Σ=1.98(Si_2.42Ti_0.24Fe_0.18Al_0.14)_Σ=2.98O₁₂OH_0.11. Ti-rich garnets are not common and their crystal chemistry is still under investigation. The present work presents new evidence that will enable the elucidation of the structural chemistry of Ti- and Cr-rich garnets.     

勃姆石的热相变及其降氟作用研究

笔者于1985年春,发现了我国迄今报道的品位最高的勃姆石矿。将勃姆石在650℃下焙烧0.5—1h,则可相变生成γ-Al₂O₃,其比表面积最大,利用这样的γ-Al₂O₃,可以有效地除去水中过量的氟。该工艺的水处理费用较低,有可能为高氟水地区的饮水降氟提供一条新途径。     

The disproportionation of andalusite (Al2SiO5) to Al2O3 and SiO2 under shock compression

Shock-recovery experiments have been carried out on andalusite single crystals of gem quality in a pressure range from 300 up to 575 kbar. Infrared spectroscopic investigations indicate a progressive shock-induced transformation of andalusite into short-range-ordered Al₂O₃ and SiO₂ phases within a pressure interval from ～360 to ～575 kbar. Exposure to dynamic pressures of about 575 kbar results in andalusite breaking down into incoherently crystallized γ-Al₂O₃, well-crystallized α-Al₂O₃ and X-ray amorphous SiO₂. The shock disproportionation of andalusite is presumed to take place in three separate stages of reaction. The comparison of shock-induced reactions with results from static experiments on kyanite indicates significant differences in the transformation pressures and in the mechanism of the high pressure decomposition.     

Oxidation of Mn(II): Initial mineralogy,oxidation state and ageing

The initial solid phase oxidation products formed during the oxidation of aqueous Mn(II) at 25°C were studied as a function of time. The analyses included morphology (TEM), mineralogy (x-ray diffraction), $\text{O}\text{Mn}$ ratio (iodometric method), oxidation state of manganese (XPS), and dissolved manganese. The initial solid formed under our conditions was Mn₃O₄ (hausmannite) which converted completely to γMnOOH (manganite) after eight months. βMnOOH (feitknechtite) appeared to be an intermediate in this transformation. The $\text{O}\text{Mn}$ ratio was initially 1.37 and increased to 1.49 over the same time span. Throughout the course of this study the XPS analyses showed that the surface of the solids (<50 Å) was dominated by Mn(III). The solution pH and dissolved manganese concentrations were consistent with disproportionation and oxidation reactions that favor the transformation of Mn₃O₄ to γMnOOH but not to γMnO₂.     

Crystal structures of the Rb- and Sr-exchanged forms of ivanyukite-Na-T

The Rb- and Sr-exchanged forms of ivanyukite have been obtained and structurally characterized. The chemical formulas derived from the electron microprobe data are as follows: the Rb-exchanged form (Na_0.10K_0.07Ca_0.15Sr_0.05Rb_1.81Ba_0.02)_{Σ = 2.20}[(Ti_3.65Nb_0.19Fe_0.05Mn_0.01)_{Σ = 3.90}O_2.07/(OH)_1.93(Si_2.98Al_0.02)_{Σ = 3.00} O₁₂] · 3.61H₂O; the Sr-exchanged form (K_0.03Sr_0.81Ca_0.04Ba_0.07)_{Σ = 0.95}[(Ti_3.74Nb_0.19Fe_0.03)_{Σ = 3.96}] [O_1.83/(OH)_2.17](Si_2.99Al_0.01)_{Σ = 3.00}O₁₂) · 7H₂O. The structures of the Rb- and Sr-exchanged forms of ivanyukite have been solved and refined using the least squares method. The structures are based on a mixed three-dimensional octahedral-tetrahedral framework of the pharmacosiderite type with channels occupied by Rb⁺ and Sr²⁺ cations and water molecules. The Rb⁺ cations in the Rb-exchanged form are 12-coordinated, whereas the Sr²⁺ cations in the Sr-exchanged form are 9- or 7-coordinated. The statistical investigation of the geometric parameters of the pharmacosiderite-type titanosilicates showed that symmetry changes are associated with the interactions of extraframework cations with the O atom of the Ti₄(O,OH)₄ clusters of the titanosilicate framework. The relationship between the unit-cell parameters in titanosilicates of the pharmacosiderite type and the structural geometric parameters of the titanosilicate framework has been proved by the use of multiple regression equations.     

Aromatic volatile organic compounds and their role in ground-level ozone formation in Russia

This paper reports proton mass spectrometry data on aromatic volatile organic compounds (VOCs) (benzene, toluene, phenol, styrene, xylene, and propylbenzene) obtained in different Russian regions along the Trans-Siberian Railway from Moscow to Vladivostok, based on expedition data retrieved using the TRO-ICA-12 mobile laboratory in the summer of 2008. The contribution of aromatic VOCs to ozone formation in the cities and regions along the measurement route has been estimated quantitatively. The greatest contribution of aromatic VOCs to ozone formation is characteristic of large cities along the Trans-Siberian Railway (up to 7.5 ppbv O₃) specified by the highest concentrations of aromatic VOCs (1–1.7 ppbv) and nitrogen oxides (>20 ppbv). The results obtained are indicative of a considerable contribution (30–50%) of anthropogenic emissions of VOCs to photochemical ozone generation in the large cities along the Trans-Siberian Railway in hot and dry weather against the background of a powerful natural factor such as isoprene emissions controlling the regional balance of ground-level ozone in warm seasons.

     

High-pressure phase relations in the system TiO2–ZrO2 to 12?GPa: stability of αPbO2-type srilankite solid solutions of (Ti1?x , Zr x )O2 (0?≤?x?≤?0.6)

Phase relations in the system TiO₂–ZrO₂ were examined in the pressure range of 3.5–12?GPa at 1,800?°C, using multianvil apparatus. At 1,800?°C, TiO₂ rutile transforms to αPbO₂ structure at 10?GPa, and the αPbO₂-type solid solution is stable in compositional range between TiO₂ and about (Ti_0.6, Zr_0.4)O₂ at 3.5–12?GPa. Combination of the present results with the published data at 0–3?GPa demonstrates that continuous solid solution with the αPbO₂-type structure is stable between TiO₂ and (Ti_1?x , Zr _x )O₂ (x?≈?0.6) at 0–12?GPa. This indicates that both the αPbO₂-type TiO₂ and srilankite Ti₂ZrO₆ with the same structure belong to the continuous solid solution system though the two phases have been regarded as different minerals. With increasing ZrO₂ content, lattice parameters of a- and c-axes of the αPbO₂-type solid solution increase, but b-axis is almost constant or slightly decreases. At higher pressure, the αPbO₂-type solid solution dissociates into two phases, αPbO₂-type phase and tetragonal zirconia. Srilankite with more TiO₂-rich composition than Ti₂ZrO₆ might be found in natural rocks derived from the deep upper mantle.     

Viscosity of liquid silica,silicates and alumino-silicates

Viscosity measurements are reported for amorphous silica and liquids belonging to the systems SiO₂-M, SiO₂-Al₂O₃-M, where M is an alkali-earth metal oxide, MnO, or alumina, and the systems SiO₂-“FeO”, SiO₂-FeO-Fe₂O₃-CaO, and SiO₂-Al₂O₃-N, where N = Na₂O or K₂O. The implications of these measurements concerning the coordination of Al and the structure of these liquids are briefly discussed. Stable liquids in the systems SiO₂-Al₂O₂-M show a non-Arrhenian temperature dependence of their viscosity, in general. Results obtained with empirical methods to calculate the viscosity of silicate liquids are compared with our observations.     

Remediation of colloid-facilitated contaminant transport in saturated porous media treated by nanoparticles

Facilitation of contaminant transport in porous media due to the effect of indigenous colloidal fine materials has been widely observed in laboratory and field studies. It has been explained by the increase in the apparent solubility of low soluble contaminants as a result of their adsorption on the surface of fine particles. Attachment of colloidal fine particles onto the rock surface could be a promising remedy for this challenge. In this experimental study, the effect of five types of metal oxide nanoparticles, γ-Al₂O₃, ZnO, CuO, MgO, and SiO_2, on suspension transport was investigated. In several core flooding tests, different nanofluids were used to saturate the synthetic porous media. Subsequently, after sufficient soaking time, the suspension was injected into the treated porous media. Analysis of the effluent samples’ concentration by Turbidimeter apparatus demonstrated that the presence of nanoparticles on the rock surface resulted in a significant reduction in fine concentrations in the effluent samples compared with non-treated media; ZnO and γ-Al₂O₃ demonstrated the best scenarios among the tests performed in this study. In order to characterize the surface properties of the treated porous media, the zeta potential of the surface was measured. Results showed that the treated porous media acts as a strong adsorbent of fine particles, which are the main carrier of contaminants in porous media. These findings were quantitatively confirmed by calculation of the total energy of interaction between the fine particles and rock surface using the Derjaguin–Landau–Verwey–Overbeek theory.     

The spectra of hard radiation from radio pulsars

The kinetic equation for the distribution function of relativistic electrons is solved taking into account quasi-linear interactions with waves and radiative processes. Mean values of the pitch angles ψ are calculated. If the particles of the primary beam with Lorentz factors γ_b～10⁶ are resonant, then the condition γ_bψ_b?1 is satisfied, the particle distribution is described by the function f _‖(γ) ∝ γ^?4, and the synchrotron radiation spectrum is characterized by the spectral index α=3/2. On the other hand, if a cyclotron resonance is associated with particles of the high-energy tail of the secondary plasma (γ_t～10⁵), then γ_tψ_t?1, and the distribution function has two parts—f _‖(γ) ∝ γ and f _‖(γ) ∝ γ^?2—which correspond to the spectral indices α₁=+1 and α₂=?0.5. This behavior is similar to that observed for the pulsar B0656+14. The predicted frequency of the maximum ν_m=7.5×10¹⁶ Hz coincides with the peak frequency for this pulsar. The model estimate for the total synchrotron luminosity of a typical radio pulsar with hard radiation L _s =3×10³³ erg/s is in agreement with observed values.     

REE-, Zr-, and Th-rich titanite and associated accessory minerals from a kersantite in the Frankenwald, Germany

Summary The mineral chemistry of a Variscan lamprophyre (kersantite) from the Frankenwald, Germany, has been investigated by electron microprobe. This potassic, Si-saturated, mafic rock contains an assemblage of different generations of titanite and allanite-(Ce), Th-rich zircon, and metamict REE–Ti–Zr–Th silicates. The primary ferroan-ceroan titanite contains unusually high contents of REE₂O₃ (max. (ΣLa to Sm)+Y = 36.8 oxide wt.%), ZrO₂ (max. 5.4 wt.%), and ThO₂ (max. 3.1 wt.%). Its empirical formula averages to (Ca_0.31 La_0.17 Ce_0.30 Pr_0.03 Nd_0.08 Sm_0.01 Y_0.01 Fe²⁺_0.06 Th_0.02 Mn_0.01)_Σ1.00 (Ti_0.60 Fe²⁺_0.22 Al_0.06 Zr_0.07 Mg_0.04 Nb_0.01)_Σ1.00 O_1.00(Si_0.93 Al_0.07)_Σ1.00 O₄. Element correlations reveal operation of the complex substitution Ca²⁺+Ti⁴⁺+Th⁴⁺ ⇔ REE³⁺+Al³⁺+Zr⁴⁺. In comparison to allanite-(Ce), ferroan-ceroan titanite preferentially incorporated the LREE and Th. This finding is inconsistent with previous experimental studies and suggests that both minerals are not cogenetic. High Zr contents in titanite, usually known only from Si-undersaturated alkaline rocks, and the predominance of Fe²⁺ suggest that the ferroan-ceroan titanite crystallized from an alkali-rich, low-fO₂ residual melt.     

应用电子微探针-扫描电镜-拉曼光谱-电子背散射衍射研究一种未知Ti-Zr-U氧化物的矿物学特征

本文应用电子微探针(EPMA)、扫描电镜(SEM)在阿尔金地区的榴闪岩中发现了一种微米级含铀氧化物矿物,结合光学显微镜、拉曼光谱和电子背散射衍射(EBSD)技术对该矿物的化学成分、赋存状态、物理及光学性质、晶体结构等矿物学特征进行了研究。结果表明,该矿物在空间上与钛铁矿关系密切且主要产于其边部,为一种不透明矿物;主要化学组成为TiO2、ZrO2和UO2,实验化学式为(Zr,U)Ti2O6,其中U与Zr互为类质同象替代;具独特的拉曼光谱特征,初步确定为斜方晶系且具有序的铌钙矿结构。通过电子微探针U-Th-Pb定年获得等时线年龄为451±49Ma,可能代表了寄主岩石的退变质年龄。将该矿物与化学成分类似的晶体进行对比,发现与斯里兰卡石等已知天然矿物存在差异,而与一种人工合成晶体Zr5Ti7O24在化学成分和晶体结构上较为相似,可以初步推断Ti-Zr-U氧化物为一种未被人们发现的新矿物。     

Studies on tapiolite from Arehalli pegmatite, Hassan District, Karnataka

Tapiolite hosted in lithium-caesium-tantalum (LCT)-type granitic pegmatite, near Arehalli, of Holenarsipur schist belt (HSB), occurs as euhedral crystals within the muscovite books or in association with columbite-tantalite. In this study, compositional and crystallographic characteristics of the tapiolite are presented. The tapiolite is Ta-rich (79.8% Ta₂O₅) and also Fe-rich (13.1% FeO) with minor amounts of Nb (3.80% Nb₂O₅) and Mn (0.30% MnO₂), and is a Fe-end member of the FeTa₂O₆-MnTa₂O₆ series, ferrotapiolite. The tapiolite has very restricted compositional range. Calculated structural formula of the investigated tapiolite is [(Fe_0.27 Mn_0.66)_0.93 (Nb_0.45 Ta_1.57 Ti_0.004 Sn_0.03)_2.027O₆].     

Oxidative removal of Mn(II) from solution catalysed by the γ-FeOOH (lepidocrocite) surface

A laboratory study was undertaken to ascertain the role of surface catalysis in Mn(II) oxidative removal. γ-FeOOH, a ferric oxyhydroxide formed by O₂ oxidation of ferrous iron in solution, was studied in the following ways: surface charge characteristics by acid base titration, adsorption of Mn(II) and surface oxidation of Mn(II). A rate law was formulated to account for the effects of pH and the amount of surface on the surface oxidation rate of Mn(II). The presence of milli-molar levels of γ-FeOOH was shown to reduce significantly the half-life of Mn(II) in 0.7 M NaCl from hundreds of hours to hours. The numerical values of the surface rate constants for the γ-FeOOH and that reported for colloidal MnO₂ are comparable in order of magnitude.